Originally Posted by motogon
Because on dirt bike you have to move to balance a lot, if you don't have enough flexibility or you have restrictive gear you will fall A LOT!
That's why dirt bikes have tiny narrow seats - it's not for seating
You are confusing flexibility and perceived protection with top tier motocrossers of old, who feel invincible. Many (nowdays) wear very expensive Titanium braces and CE approved pressure suits under their pants and jerseys.
The old plastic chest protector was more for "Roost" protection, it provides very little in terms of hitting the ground.
I wear more protective (and restrictive) gear off-road than I do on-road and I wear a "Stich" (1pc Roadcrafter) with back-protection inserted in it. I don't put allot of faith in some of the foam pads clothiers put in their garments. I wear them for abraision resistance.
I wear good gloves, MC boots and the best helmets I can afford.
I tried all the other methods in crash testing - Blue jeans, t-shirts, short-sleeve shirts and all sorts of MX gear.
Not crashing will protect you the most!